﻿<p>The <em>IfcURIReference</em> provides for identifying a Uniform Resource Identifier (URI). A URI can be classified as a locator or a name or both, that is it may comprise a Uniform Resource Locator (URL) and/or a Uniform Resource Name (URN).</p>
<ul>
<li>A Uniform Resource Locator, URL, is a string conforming to a standardized format, which refers to a resource on the internet (such as a document or an image) by its location.</li>
<li>A Uniform Resource Name, URN, is intended to serve as persistent, location-independent resource identifier and is
designed to make it easy to map other namespaces (that share the properties of URNs) into URN-space.</li>
</ul>

<blockquote class="note">
NOTE&nbsp; See <a href="../../../bibliography.htm#RFC-3986">RFC 3986</a> for definition of Uniform Resource Identifier.
</blockquote>
<blockquote class="history">
HISTORY&nbsp; New defined datatype in IFC4.
</blockquote> 